This invention relates generally to the production of kinescopes and particularly to an apparatus for thumping and fluid flushing kinescope funnels to reduce blocked apertures and electron gun shorts in such kinescopes.
The kinescope, or picture tube, for a color television receiver includes a phosphor screen which is composed of alternating stripes of phosphors, each of which emits a different color of light when impacted by electrons. The phosphor stripes are produced on the faceplate panel by coating the inside surface of the panel with a slurry of one of the phosphors. A thin metal apertured shadow mask, which is supported on a sturdy metal frame, is inserted into the panel. The panel is fritted onto a funnel, and an electron gun is mounted in the neck of the funnel. The funnel is then evacuated and sealed.
In the operation of a kinescope, an electron beam is provided for each of the three primary colors red, green and blue. The three electron beams converge at the shadow mask and pass through the apertures in the shadow mask so that each beam impacts a phosphor of the proper light emitting color. The shadow mask apertures are quite small and therefore small airborne contaminants, such as glass particles, metal flakes, dust particles, small fibers, etc. can easily block an aperture and cause a dark spot on the kinescope screen during the operation of the tube. Additionally, during the operation of the kinescope, the screen and the shadow mask within the panel/frame assembly are scanned by electrons so that any particles which previously adhered to the screen or shadow mask are charged with a negative polarity. The screen and shadow mask are operated at a high positive potential so that the charged particles have a tendency to adhere to the shadow mask, thereby greatly increasing the probability of blocked apertures. The panels and funnels are fritted together by heating them to an elevated temperature in a lehr. When the funnels leave the lehr they cool and pull air in. This greatly enhances the possibility of airborn particles being pulled in and causing blocked apertures. For these reasons there is a need for an apparatus for removing the maximum number of small particles from the funnels of kinescopes prior to the insertion of the electron gun into the funnels. The instant invention is directed to such an apparatus.